Smell is thought to play an important role in sexual attraction
The study, published in the journal Human Reproduction, measured the ability of women to detect distinctive smells such as musk - while taking and not taking the Pill.
They found that women who were not taking the Pill experienced rises and falls in their ability to sense smells, corresponding to particular stages in their monthly cycles.
It has long been thought that this increase in sense of smell may be linked to libido, helping increase it at the point of the cycle in which fertilisation is possible.
However, when the women took the contraceptive pill, which uses hormones to artificially control the cycle, their sense of smell was altered throughout.
Instead of the fluctuation between different phases of the cycle, the women tested had no change day to day.
Reduced smell-sense
Their general level of smell perception matched that experienced by women not taking contraceptives who were in the pre-menstrual, or luteal phase, just before a woman begins her period.
Whether this blunting of sense of smell has a direct effect on libido is not known.
In all the researchers looked at 60 women aged 18 to 40, and asked them to try to identify six distinctive substances - anise, musk-ketone, clove, pyridine, citrus and ammonia.
The team, from University of Catania in Italy, was led by Professor Salvatore Caruso, who said that further investigations were needed.
He said: "Our data seem to show that iatrogenic steroids - such as those contained in oral contraceptives - may affect changes in smell sensitivity.
"Biologically, odours probably influence reproductive processes in humans and perhaps the notion of concealed ovulation in humans needs rethinking.
"Although our data have confirmd the existence of changes in olfactory sensitivity during oral contraceptive use with respect to non-using time, we need to carry out further studies to investigate ways in which smell variations could vary a woman's sexual life."